Anchoring devices for anchoring tendons are well known and may take many forms. Likewise, it is well known to use anchoring devices for mechanical clamping or wedging tendons, such as steel tendons or fiber reinforced polymer (FRP) tendons for structural reinforcing a structure, such as a concrete structure. The anchoring devices typically anchor the steel or FRP tendons mechanically by using pressure and friction.
The strength properties of the FRP tendons fibers in the transverse direction is poor and the mechanical anchorage has to rely on friction using large compressive stresses from the anchoring device. This introduces high principal stresses acting on the tendons in the loaded end at the distal end of the anchorage device, where both tensile and compressive forces are represented, often resulting in premature failure of the tendons.
To overcome this problem, the general practice, when anchoring flat tendons having a rectangular or square cross-section, is to use a plate-shaped anchor which is tightened in situ by varying the forces of the bolts which clamp the tendons, such that bolts at the distal end of the anchor are tightened less, to reduce the compressive forces acting on the tendons and thereby decreasing the principal stresses acting on the tendon at the distal end of the anchoring device.
However this method is difficult to manage in a controlled way.
In many cases it is desirable to provide an anchorage device which is simple in construction but yet provide a controlled grip between the anchorage device and tendons.